Providing cast-iron articles with a cell-like surface



traces of the alkali.

Patented Mar. 1939 rnovmmo CAST-IRON ARTICLES 'wrrn A CELL-LIKE summon .Iohn William Hewlett, Lymington, England No. 212,596. In Great B ritain October 7 Claims. (Cl. 148-8) This invention relates to the treatment of articles formed of cast iron, the object being to provide the article with a honeycombed or celllike surface which can retain lubricant when subjected to friction at-high temperatures and/or high pressuresJ Piston-rings, particularly for internal-combustion engines, are'found' to give very satisfactory results when treated in this. way.. Not only do 10 they quickly bed themselves in but they also prevent roughening of the cylinder bore in the early stages.

According to the invention, other article is formed of a cast iron containing more than 0.15% of phosphorus and is chemically treated so that the material, within the polygonal network formed by the phosphorus-rich con-,

stituent, is removed to some'extent, leaving the phosphorus-rich constituent in relief.

A preferred method according to the tion, involves subjecting the article:--

(a) To a neutral or acid solution ofa copper salt until it is coated with a layer of copper;

(b) After rinsing and drying, to an acid solution which will dissolve the copper coating, and

then

(c) To an alkaline, solution which will neutralize the acid adhering to the article.

Thereafter the article is washed to remove 20 inven- The invention particularly involves a pistonring provided with a cell-like surface by treatment in this manner.

In a simple method of carrying out the invention, as applied to a piston-ring of a cast iron containing the necessary content of phosphorus, the piston-ring is tie-greased in the first instance andthen placed in a neutral or acid solution of copper chloride for a predetermined time until a 40 layer of copper forms over the piston-ring. Alternatively, use may be made of other copper salts, such as copper sulphate, which will deposit copper when iron is placed in the solution. Other salts may be preesnt as long as their presence does not prevent deposition of the copper. Furthermore, the piston-ring may, if desired, be placed i a neutral solution of the copper salt in the first instance and then immersed in an acid solution of the salt. Moreover, the deposition may be accelerated by electrolytic methods.

After the piston-ring has been coated with copper in this way it is rinsed in water, alcohol or other liquid and then dried. It is then placed in a copper-dissolving acid; and for this purpose concentrated nitric acid is very satisfactory as a piston-ring or.

it dissolves the copper adhering to the ring. acid has been used a s No Drawing. Application June 8, 1938, Serial without attacking the iron.

.Thereafter the piston-ring is immersedin an alkaline solution which will neutralize the acid When concentrated nitric olution of sodium carb in water is very satisfactory for this purpose.

Thereafter the ring is washed in water, alcohol,

or other liquid to remove the traces of alkali.

Amicroscopic examination of tile surface of become cell-like.

onate 5 an article thus treated'shows that'th surface has 10 The reason to be that the phosphoruserich constituent of the cast -iron exists as a polygonal network varying in amount with'the quantity of phosphorus present, and it is the remaining constituents of th'e cast ironwithin' this network whichare removed to some extent.

The extent to which they'are removed may be controlled as desired by variation of the solution concentrations, of the time during which the articleis of the temperature of in the solutions, and 2 the solutions. Finally the phosphorus-rich constituent stands out to a greater or less extent The minute superficial cavities formed.

in relief to the mass.

ton-rings in this manner will hold the lubricant 2 in conditions of high temperature and external pressure which would remove oil from between polished surfaces not In the past it has internal-combustion engines and in steam engines so treated.

been common practice in to have cast-iron piston-rings working -in cylinders or cylinder liners made of cast iron or steel. To prevent wear of the piston rings and of the cylinders or cylinder friction it is necessary that there 35 be a film of oil or lubricant berings and the cylinder wall.

power loss by should always tween the piston liners and to reduce Recent improvements in the hardness and strength of cylinder wall material to cope with increased working pressures, higher speeds and 40 higher working temperatures permit and have led to the use of piston-rings and cylinder walls in a highly polished state. It

is also necessary to finish piston-rings and cylinder walls by fine turning or grinding or lapping to ponents to required taken that, the closer the working tolerances, so

the higher degree of polish is attained. But

highly polished surfaces in opposition are not conduc ive to the maintenance of an oil film. Provided that an oil film hereinbefore describe can be maintained between the opposed metals such as between piston-rings and cylinder wall, wear cannot'tak'e appreciable degree and by means of the process place to any dthe surface of castiron produce com- 45 dimensions and it may be can be prepared in such e manner as to provide, as stated, minute superficial cavities which hold oil in conditions of high-1. temperature and ex ternal pressure which would remove oil from be tween polished surfaces not so treeted.

What I claim as my invention and desire to secure by Letters Patent of the United. States is:

1. A method of treating an article formed or" cast iron containing more than 0.15% of phosphorus, to provide it with. a cell-like surface which can retain lubricant when. subjected to friction at high temperatures or at high pressures, which involves the following stepsz-de greasing the article. subjecting it to e solution of copper chloride until it is coated with a, layer of copper, rinsing and drying it, subjecting it to nitric acid untll the copper has been dissolved, subjecting it to an alkaline solution which will; neutralize the acid edhcrlug to it, and then washing it to remove traces of the alkali.

2. A method of treating on article formed of cast iron containing more than 6.15% of phos- IlhOlllS, to provide it with e cell-llke surface which can retain lubricant when subjected to friction at high temperatures or at high pres= sures, wl'lich involves the following steps:-subjecting the article to e solution of a, copper salt until it is coated with alover of copper, then to an acid solution which will dissolve the copper, and then to an alkaline solution wluch will neutrallze the acid adhering to it. 3. A method of treating on article formed of cast iron containing more than 0.15% of phos-: phorus, to provide it with is cell llke surface which can retain lubricant when subjected to friction at high temperatures or at high pressures, which involves the following steps? subjecting the article to a solution of copper chloride until it iscoated with a layer of copper, and then subjecting' it to an acid solution which will dissolve the copper.

4. A method of treating on article formed of cast iron containing more than 0.15% ofphosphorus, to provide it with e ce1l-like cus om phorus, to provide it with o cell-like surface which can retain lubricant when subjected to friction at high temperatures or at high pressures, which involves the following steps: subjecting the article to a solution of e copper salt until it is coated with e layer of copper, and then subjecting it to a solution of nitric acid until the copper has been dissolved.

5. A method of treating an article formed of cast iron containing more than 0.15% of phos surface which can retain lubricant when subjected to friction at high temperatures or at high pres-= sures, which involves the following" steps:-- subjectlng the article to a solution of o copper salt until it is coeted with e. lover of copper, then to a solution of nitric acid until the copper has been dissolved, and then to an aqueous solution of sodium carbonate.

6. A pistomring formed of cast iron containing more than 0.15% of phosphorus and having a polygonal network formed by the phosphorus rich constituent, said ring having a ce1l-like our face-formed by the ring being treated chemically by the ring being subjected to a solution of a copper salt until it is coated with. to layer of copper and then subjected to on acid solution which will dissolve copper so that the material within the polygonal network, formed by the: phosphorus-rich constituent, will be removed to some extent to leave the phcsphorusq'ich constituent in relief.

7. A piston-ring formed of cast iron containing: more than 0.15% of phosphorus and having" apolygonal network formed by the phosphorus rich constituent, said ring being treated chemically as specified in claim 2 so that the material within the polygonal network formed by the phosphorus-rich constituent will be removed to some extent to leave the phosphorus-rich constltuent in relief, thus providing a cell-like surface.

JOHN W. HOWLE'I'I'. 

